A. S. Liubimova

Cutting fluids are the main source of oily wastewater in the metalworking industry. This study deals with the development of antifouling composite hydrophobic membranes for treatment of oily wastewater. The novelty of this study is that a low energy electron-beam deposition technique was applied for a polysulfone (PSf) membrane with a molecular-weight cut-off of 300 kDa, which is promising for use in the treatment of oil-contaminated wastewater, by using polytetrafluoroethylene (PTFE) as target materials. The effect of the thickness of the PTFE layer (45, 660, and 1350 nm) on the structure, composition, and hydrophilicity of membranes was investigated using scanning electron microscopy, water contact angle (WCA) measurements, atomic force microscopy, and FTIR-spectroscopy. The separation and antifouling performance of the reference and modified membranes were evaluated during ultrafiltration of cutting fluid emulsions. It was found that the increase in the PTFE layer thickness results in the significant increase in WCA (from 56° up to 110–123° for the reference and modified membranes respectively) and decrease in surface roughness. It was found that cutting fluid emulsion flux of modified membranes was similar to the flux of the reference PSf-membrane (7.5–12.4 L·m⁻²·h⁻¹ at 6 bar) while cutting fluid rejection (R_CF) of modified membranes increased compared to the reference membrane (R_CF = 58.4–93.3% for modified and R_CF = 13% for the reference PSf membrane). It was established that despite the similar flux of cutting fluid emulsion, modified membranes demonstrate 5–6.5 times higher flux recovery ratio (FRR) compared to the reference membrane. The developed hydrophobic membranes were found to be highly efficient in oily wastewater treatment.

Тонкопленочные композиционные мембраны (ТКМ) для ультрафильтрации с низким номинальным молекулярно-массовым пределом отсечения были получены при введении добавок фуллеренола C₆₀(OH)₂₄ в селективный полиамидный (ПА) слой, сформированный методом межфазной поликонденсации при использовании в качестве подложки половолоконной ультрафильтрационной мембраны на основе полисульфона. Межфазную поликонденсацию с образованием тонкого полиамидного слоя проводили при последовательной фильтрации раствора триэтилентетрамина (ТЭТА) в воде и раствора изофталоилхлорида в гексане через половолоконную мембрану. При увеличении концентрации фуллеренола в водном растворе ТЭТА угол смачивания селективного слоя уменьшается с 34 до 21°. Показано, что устойчивость к засорению ТКМ ПА/фуллеренол выше, чем исходной немодифицирован- ной мембраны. Мембраны, полученные с использованием 0,3–0,75 % дисперсий фуллеренола в растворе ТЭТА, характеризовались максимальным значением восстановления потока после фильтрации раствора лизоцима.

The effect of the component ratio on the permeability and contact angle of ultrafiltration polysulfone hollow fiber membranes modified by interfacial polycondensation of triethylenetetramine (TETA) and isophthaloyl chloride (IPC) has been studied. It has been found that the dependence of the rejection factor on the monomer ratio in the TETA: IPC range from 1: 28 to 20: 1 has two peaks. The first rejection peak is observed in a narrow range of TETA: IPC ratios close to 7: 1. The second peak is observed in a rather broad range of isophthaloyl chloride excess, at TETA: IPC equivalent ratios 1: (5–15). The membrane pure water flux was shown to change conversely to the rejection coefficient. The influence of the average functionality of the system on the change in the selectivity of the modified membranes was studied. A correlation between hydrophilicity and permeability of the modified membranes was revealed: with decreasing contact angle the pure water flux enhances, and the rejection coefficient decreases.